Emerson Enhancement Effect
by /u/SuperAngryGuy of /r/HandsOnComplexity
The Emerson effect is about driving photosynthesis with part of the light PAR (400-680nm in this case), and part of the light far red color (700nm-740nm or so wavelength), which combined can result in photosynthesis rates higher than normal.
Several recent studies have shown that far-red photons synergistically interact with shorter wavelength photons to increase leaf photochemical efficiency. (source)
Robert Emerson used his work with red and far red light to deduce that there must be two photosystems, called photosystem I (PSI) and photosystem II (PSII). These are named in the order of discovery, but for photosynthesis the process starts with the PSII first. Monochromatic light has a sharp drop off in photosynthesis at 680nm or so (red drop effect), but this does not happen if far red light is added with about 720nm being most efficient in driving additional photosynthesis.
Adding far-red photons (up to 40%) to a background of shorter wavelength photons caused an increase in canopy photosynthesis equal to adding 400-700nm photons. Far-red alone minimally increased photosynthesis. This indicates that far-red photons are equally efficient at driving canopy photosynthesis when acting synergistically with traditionally defined photosynthetic photons.These results suggest that farred photons (701-750 nm) should be included in the definition of photosynthetically active radiation. Shuyang Zhen and Bruce Bugbee, Far-red photons have equivalent efficiency to traditional photosynthetic photons.
Key Takeaways
- Far red light can drive the PSI independently of the PSII, and PAR is more efficient with the PSII while not as well excited with the PSI. Basically how the Emerson effect works is freeing up electrons between the PSI and PSII by driving them more efficiently in parallel, and photosynthesis becomes more efficient as a result.
- You can see this jamming of electrons in chlorophyll fluorescence shots with proteins associated with the PSII and much less fluorescence associated with the PSI (the single 750nm hump). Higher fluorescence means lower photosynthesis efficiency.
- I think most far red driver boards are gimmicks because they are likely not putting out enough far red light to make a noticeable difference.
- Learn more about how different light colors affect plants »
View related studies and papers (44)
- Far-red: The Forgotten Photons YouTube vid by Bruce Bugbee, Utah State
- Far-red photons have equivalent efficiency to traditional photosynthetic photons: implications for re-defining photosynthetically active radiation.
- Photosynthetic activity of far-red light in green plants
- The effect of far-red light on the productivity and photosynthetic activity of tomato
- The long-wavelength limit of plant photosynthesis
- Far‐red radiation stimulates dry mass partitioning to fruits by increasing fruit sink strength in tomato
- Plant responses to red and far-red lights, applications in horticulture
- Growth and Cell Division of Lettuce Plants under Various Ratios of Red to Far-red Light-emitting Diodes
- Supplemental Far-Red Light Stimulates Lettuce Growth: Disentangling Morphological and Physiological Effects
- Effects of the red:far-red light ratio on photosynthetic characteristics of greenhouse cut Chrysanthemum
- Disentangling the effects of photosynthetically active radiation and red to far-red ratio on plant photosynthesis under canopy shading: a simulation study using a functional–structural plant model
- Dissecting the Genotypic Variation of Growth Responses to Far-Red Radiation in Tomato
- The photosynthetic parameters of cucumber as affected by irradiances with different red:far-red ratios
- Growth and nutritional properties of lettuce affected by mixed irradiation of white and supplemental light provided by light-emitting diode
- Promotion of Flowering from Far-red Radiation Depends on the Photosynthetic Daily Light Integral
- Increase in Biomass and Bioactive Compounds in Lettuce under Various Ratios of Red to Far-red LED Light Supplemented with Blue LED Light
- Effects of Continuous or End-of-Day Far-Red Light on Tomato Plant Growth, Morphology, Light Absorption, and Fruit Production
- Effect of supplemental far-red light with blue and red LED lamps on leaf photosynthesis, stomatal regulation and plant development of protected cultivated tomato
- Far-red light is needed for efficient photochemistry and photosynthesis
- Far-Red Light Accelerates Photosynthesis in the Low-Light Phases of Fluctuating Light
- Effect of interactions between light intensity and red-to*far-red ratio on the photosynthesis of soybean leaves under shade condition
- The role of far-red light (FR) in photomorphogenesis and its use in greenhouse plant production
- Action spectra of photosystems II and I and quantum yield of photosynthesis in leaves in State 1
- Far-Red Spectrum of Second Emerson Effect: A Study Using Dual-Wavelength Pulse Amplitude Modulation Fluorometry
- Defining the Far-Red Limit of Photosystem II in Spinach
- Far-red radiation promotes growth of seedlings by increasing leaf expansion and whole-plant net assimilation
- Fast cyclic electron transport around photosystem I in leaves under far-red light: a proton-uncoupled pathway?
- The phytochrome red/far-red photoreceptor superfamily
- A Moderate to High Red to Far-red Light Ratio from Light-emitting Diodes Controls Flowering of Short-day Plants
- Overhead supplemental far-red light stimulates tomato growth under intra-canopy lighting with LEDs
- Morphological and physiological properties of indoor cultivated lettuce in response to additional far-red light
- Far-red light enhances photochemical efficiency in a wavelength-dependent manner
- Far-red light during cultivation induces post harvest cold tolerance in tomato fruit
- Supplemental intracanopy far-red radiation to red LED light improves fruit quality attributes of greenhouse tomatoes
- Plant responses to red and far-red lights, applications in horticulture
- Blue radiation attenuates the effects of the red to far-red ratio on extension growth but not on flowering
- Supplemental Far-red Light-emitting Diode Light Increases Growth of Foxglove Seedlings Under Sole-source Lighting
- The effect of far-red light on the productivity and photosynthetic activity of tomato
- The Effect of Supplemental Blue, Red and Far-Red Light on the Growth and the Nutritional Quality of Red and Green Leaf Lettuce
- Substituting green or far-red radiation for blue radiation induces shade avoidance and promotes growth in lettuce and kale
- A Mathematical Model of Photosynthetic Electron Transport in Response to the Light Spectrum Based on Excitation Energy Distributed to Photosystems
- Duration of light-emitting diode (LED) supplemental lighting providing far-red radiation during seedling production influences subsequent time to flower of long-day annuals
- Improvement of Growth and Morphology of Vegetable Seedlings with Supplemental Far-Red Enriched LED Lights in a Plant Factory
- Effect of Extended Photoperiod with a Fixed Mixture of Light Wavelengths on Tomato Seedlings